The present invention relates to freeze indicators, thaw indicators and thaw/refreeze indicators based on rapid reactions in the solid state. More specifically, the present invention is related to a freeze indicator based on diacetylenes that can monitor and indicating freezing, thawing and if a material has been thawed and refrozen.
Many perishables, such as sera and vaccines get spoiled, deteriorate or lose quality if they suffer even a brief exposure to a temperature near or below freezing. Many types of produce, such as bananas, turn brown and become mushy. Some flowers, salad greens and herbs, wilt or shrink and become dark colored, useless and/or unappealing when exposed to freezing or near-freezing temperatures.
Biological products, such as vaccines, when used in hot climates, are commonly protected from excessive temperature exposure by keeping them in portable cold storage containers using blue ice or equivalent measures. However, such measures run the risk of causing freeze-related damage to vaccine samples in the vials or syringes from the cold ambient temperatures. Deterioration of vaccines, such as Hepatitis B vaccine is one example.
Though people feel cold temperatures it is difficult to determine when the skin or body part has had frost bite. An early warning indicator or coating can help eliminate frostbite and adverse conditions caused by exposure to cold temperatures.
Other examples where cooling beyond the freezing point has a detrimental effect include foods such as mayonnaise, fabric softeners, latex products such as paints, concrete modifiers and laboratory supplies. Biological samples such as whole blood, insulin and the like can be seriously affected when subjected to freezing conditions, and this is also true for high value biotechnology drugs containing proteins, enzymes or peptides. Therefore, it is important to the seller, buyer and end user of such products that some indicator be provided which will signal cooling conditions which could trigger a change in certain products.
A variety of freeze indicators are developed or proposed. For example, Hanlon et al. U.S. Pat. No. 4,148,748 proposes a freeze indicator which includes a means for detecting a freeze/thaw cycle by the encapsulation of an opaque colloidal dispersion of organic solid particles, such as latexes, suspended in a liquid medium. After having been frozen and thawed the suspension coagulates to form a non-flowing waxy gel leaving a clear liquid. The organic colloidal dispersion has no inherent color and appears as a white opaque cloudy liquid. Therefore, it presents serious problems in observing a change in state due to a freeze/thaw cycle.
Johnson in U.S. Pat. No. 4,191,125 discloses a freeze indicator composed of a frangible ampoule substantially filled with a mixture of water, a nucleating agent and a surfactant. Upon reaching the freezing point of water, the water mixture freezes fracturing the frangible ampoule.
Johnson in U.S. Pat. No. 4,646,066 discloses an indicator device employing a tuned electrical circuit interrogatable by an RF signal in the microwave range, or lower, based on the rupturing of saline-containing microcapsules or de-emulsification of liquids.
Emslander et al. in U.S. Pat. No. 4,846,095 disclose a freezing point indicating device comprising a microporous sheet which is wetted by a freeze-sensitive mixture of at least two liquids such as a water/butanol mixture. When the temperature of the liquid mixture reaches a critical value, such as the freezing point of water, the optical properties of the microporous sheet change.
Ignacio et al. in U.S. Pat. No. 5,239,942 disclose a freeze indicator comprising a frangible ampoule which is rupturable to release a dye that provides a color change.
Pereyra in U.S. Pat. No. 5,964,181 discloses a critical temperature indicating device employing an indicating composition which includes an organic compound that has a freezing point above the critical temperature; a compound that has a freezing point below the critical temperature; and a wetting component that can wet out a microporous membrane at about the critical temperature upon solidification of a portion of the composition.
Shahinpoor in U.S. Pat. No. 6,837,620 discloses a shape memory alloy temperature sensor having an alloy element that changes shape when exposed, even temporarily, to temperatures below a particular start temperature to provide a persistent indication of the temperature exposure.
U.S. Pat. No. 6,957,623 discloses a means for detecting a freeze/thaw cycle by the encapsulation of a mixture of water, a nucleating agent, latex, and stabilizers which is translucent prior to freezing and opaque after thawing.
Guisinger in U.S. Pat. No. 6,957,623 describes a critical temperature indicator which produces a visual, irreversible indication that the indicator has been exposed to a critical temperature, such as a temperature near the freezing point of water. The device includes a transparent housing and a temperature sensitive transformable material contained within the transparent housing. The transformable material includes a mixture of water, a nucleating agent, latex, and a stabilizer for the nucleating agent.
Taylor at el. in U.S. Pat. No. 7,343,872 disclose a freeze indicator which employs, an active indicator element, a dispersion of solid particles in a liquid medium which can be water or aqueous and which coagulates to provide an irreversible appearance change when subject to freezing. The active indicator element can be a dilute colloidal dispersion of a metal, such as gold or silver or other inorganic pigment material in water or an aqueous medium.
Taylor et al. in U.S. Pat. No. 7,571,695 disclose freeze indicators employing colloidal dispersions as active elements and include flexible freeze indicators, freeze indicators protected against drying out and freeze indicators employing core shell composites, for example gold coated pigments as active indicator elements. Also disclosed are: a combination freeze indicator and threshold temperature indicator; a combination threshold indicator and cumulative temperature indicator; and three-way combination indicators that can provide indications of cumulative past temperature exposure, exposure to freezing temperatures and exposure to a temperature above a threshold.
Taylor et al. in U.S. Pat. No. 7,624,698 describe a freeze indicator which employ an active indicator element, dispersion of solid particles in a liquid medium which can aqueous and which coagulates to provide an irreversible appearance change when subject to freezing.
Kagan et al. in U.S. Application Patent No. 20100020846 disclose a temperature-threshold indicator device comprising a sealed housing containing a suspension of inorganic nanoparticles suspended in a liquid medium wherein the suspension undergoes an irreversible detectible change in optical characteristics upon freezing of the liquid medium due to aggregation of the nanoparticles.
Randall and Yeager in U.S. Patent Application No. 20100264640 disclose a device for obscuring printed indicia which includes a printable substrate, an indicia printed on a first surface of the substrate, an irreversible thermochromic material operably associated with the printable substrate which does not affect readability of the indicia when not subjected to a predetermined critical temperature and when subjected to the predetermined critical temperature renders the indicia unreadable by virtue of a color change surrounding the indicia.
Palin and Cimbalova in U.S. Patent Application Nos. 20090211268 and 20090139250 disclose a defrost indicator configured such that the process of freezing and defrosting the defrost indicator places the defrost indicator into a state that is not completely reversed by refreezing, so that one can detect whether the defrost indicator defrosted and refroze or never defrosted by observing its current state.
Other representative patents on freeze-thaw type indicators include U.S. Pat. Nos. 3,615,719; 4,114,443; 4,145,918; 4,148,748; 4,191,125; 5,111,768 and 5,239,942.
Preziosi et al. in U.S. Pat. No. 4,892,677 disclose a process for monitoring the time-temperature history of perishable items. The process initially involves forming a solution comprising diacetylenic monomer and a solvent. The solution is frozen and the frozen solution having crystalline diacetylenic monomer therein is irradiated to partially polymerize the diacetylenic monomer. Irradiation is required because diacetylenes polymerize very slowly, often days and months for development of a faint color at lower temperatures, such as 0° C. Due to the intensity of the color of the polydiacetylene formed upon radiation, the entire article of manufacture appears to be colored. Upon exposure to temperatures above a critical temperature, the frozen solvent melts and extracts unreacted monomer from the colored polymer, thereby causing a sharp color transition which indicates that the perishable should possibly be discarded. U.S. Pat. Nos. 4,735,745; 5,685,641 and 5,695,284 also utilize a diacetylene as an indicator. This type of indicator undergoes a color change when the product temperature undesirably exceeds about 0° C., i.e., thawing. The device of Preziosi et al. is unidirectional, meaning it is capable of providing a signal with an increase in temperature. These devices monitor thawing only and not freezing. As the frozen solution of diacetylene does not develop color rapidly, the devices proposed by Preziosi et al. require radiation for polymerization of diacetylenes to color polymer which is undesirable.
Patel in U.S. Pat. No. 6,472,214 discloses a device composed of a color changing indicator, an optional polymeric binder that can have gel-forming capability, and a solvent mixture which induces a color change in the indicator when the device is frozen, in the region of about 0 to −30° C. The color-changing indicator can be a fine dispersion of a diacetylene partially polymerized by radiation, dispersed in the solvent mixture. When the temperature of the device is lowered to the freezing point of water, an activator solvent phase separates out of the solvent mixture and induces a color change in the indicator. The device proposed by Patel also requires radiation to produce color.
Most of the prior art devices are large, complex, difficult to manufacture, expensive with a cost of up to $1 US per device, use fluids, require activation such as with UV light, use glass, have a short shelf life, do not show how long an item has been frozen, do not display color change while frozen, and none of them are self-reading. None of the prior art devices are capable of monitoring freezing, thawing and re-freezing.
The freeze indicators reported in the literature only indicate freezing and do not show how long an item has been frozen. Hence, there is a need for an indicator which shows the extent or duration of freezing. The freeze indicators reported in the literature only indicate freezing and do not indicate thawing and refreezing. Hence, there is also a need for an indicator which shows the extent of freezing and indicates thawing followed by re-freezing.
There is a need for freeze and thaw indicators which are simple, easy to make, do not require external means of activation such as radiation with UV light, which are self-activating, self-reading, which also monitor thawing and refreezing, which do not have a low viscosity fluid and are economical for commercial production.